The particular test gas or measuring gas must be admitted to electrochemical gas sensors at regular intervals for checking the function or for calibration. This happens in practice, in general, manually from pressurized gas containers or with calibrating gas containers under normal pressure or also automatically by means of chemical or electrochemical gas generators, as is described, for example, in GB 2 254 696 A. The common feature of these processes is that the electrochemical gas sensor is not ready for measurement during the calibration.